An intake system for the supply of fresh air of an internal combustion engine is usually equipped with an air mass sensor, by means of which a motor control cooperates, in order to be able to operate the internal combustion engine according to requirements. For example, parameters for the fuel injection, for a throttle valve, for valve control times, for an exhaust gas return and suchlike depend on the air mass which is supplied at a particular moment. Such an air mass sensor, which in particular can be configured as a hot film sensor, is comparatively sensitive with respect to impurities. Accordingly, the air mass sensor in the intake system is usually arranged downstream of an air filter. Furthermore, it is usual to introduce blow-by gases downstream of the air mass sensor, which are returned from a crankcase of the internal combustion engine into the intake system.
For the return of the blow-by gases, it is basically possible to connect to the intake system a hose originating from the crankcase or from a cylinder-head cover. This can entail a comparatively high expenditure.